The
mass coral bleaching event smashing the Great Barrier Reef has
severely affected more than half its length and caused patches of
bleaching in most areas, according to scientists conducting an
extensive aerial survey of the damage.

“The
good news with my last flight is that I found 50 reefs that weren’t
bleached, so that may be the southern boundary,” said Terry Hughes
from James Cook University. Hughes is the head of the national coral
bleaching task force, which has been conducting flights over the
length of the reef, mapping bleached areas and recording the severity
of the damage.

Climate
change and a strong El Niño have caused hundreds of kilometres of
the reef to bleach, as the higher water temperatures stress the
coral, and they expel their symbiotic algae. If the bleaching is bad
enough, or the temperatures remain high for long enough, the corals
die, putting the future of reefs at risk.

The
mass bleaching on the Great Barrier Reef is part of what the US
National Oceanographic and Atmospheric Administration has called the
third global bleaching event – the first occurred in 1998.

Initial
reports suggested only the most northern and remote areas of the
Great Barrier Reef were bleaching, but as aerial surveys have
continued, scientists have struggled to find a southern boundary.

The
latest find of a stretch of unaffected reefs around Mackay was a
small piece of good news, Hughes said.

But
he said its significane would be unclear until reefs further south
were examined.

“It
may be a false southern boundary,” Hughes said. The reefs around
Mackay have unusually large tides, which might have pulled in cooler
water and saved the coral there.

So
far, the surveys reveal there are severely bleached reefs almost as
far south as Cairns, and patchy bleaching almost to Mackay.

Morgan
Pratchett from James Cook University said there was some bleaching
even further south. “There is reasonable levels of bleaching as far
south as the Keppels, which is even more than we suspected
initially,” Pratchett said.

Hughes
planned to fly over another 150 reefs, creating a total of about 900
surveyed. Only then will the group have a complete picture of how bad
the bleaching is.

The
next step will be to examine how much of that bleached coral has
died. “If the corals are severely bleached, then a lot will die. If
they are lightly bleached, which is the case with a lot of reefs
south of Townsville, then they’ll regain their colour over the next
couple of months and there won’t be much mortality,” Hughes said.

Two
weeks ago, the Great Barrier Reef Marine Park Authority reported half
the coral in the northern parts of the reef were dead. Hughes said
that was consistent with reports from divers north of Port Douglas.

Hughes
said this was by far the worst bleaching event to have hit the Great
Barrier Reef. He said it was three to four times worse than in 1998
or the second great bleaching in 2002.

Last
year, the Great Barrier Reef narrowly escaped being listed as “in
danger” by Unesco, even though environmental groups said it clearly
met the criteria.

Hughes
said the “outstanding universal value” of the reef was now
“severely compromised”.

Ariane
Wilkinson, a lawyer at Environmental Justice Australia, said the
bleaching might cause Unesco to reconsider its decision.

“[Unesco]
weren’t scheduled to examine the reef this year but in light of the
terrible bleaching it is entirely possible that they may decide to
look at the reef,” she said.

“If
the World Heritage system is to have any value, it must address the
most serious threats to the most iconic examples of world heritage,”
she said. “If any site falls into this category, it is the ...
Great Barrier Reef.”

Paul Beckwith: My
Condolences to Australia's Great Barrier Reef

The
Great Barrier Reef along the NE coastline of Australia is (soon to be
was) the largest living ecosystem on Earth. It is dying, and it's
loss will be devastating for planet Earth, not to mention Australia.
Not only was the 2300 km long reef teeming with life (biological
hotspot), it protects coastlines from storms and is a World Heritage
tourist magnet. Of 520 reefs aerially surveyed, 516 were white
(bleached) and of these at least 50% will die. Loss to biodiversity
is incalculable.